Marine surveys may be used to determine the location and/or state of a hydrocarbon bearing earth formation residing below a body of water. Marine surveys using towed survey streamers may use ten or more survey streamers spaced horizontally, with the survey streamers towed behind a tow vessel and in proximity to the hydrocarbon bearing earth formation. In the related art, horizontal separation for the survey streamers is provided by two paravanes, where the paravanes develop opposing forces that tension a spreader cable as the paravanes are towed through water. Thus, a large portion of the towing force developed by the tow vessel is used just to keep the survey streamers properly horizontally spaced.
Also in the related art, each survey streamer is communicatively coupled to the tow vessel by way of a lead-in cable extending between the tow vessel and a respective location of the survey streamer on the spreader cable. While the lead-in cable for any particular survey streamer may carry little, if any, towing force, the lead-in cables themselves contribute to drag, and thus increase the amount of towing force the tow vessel must develop.
In order to ensure good reception of signals at the survey streamers, the survey streamers should be at a particular depth. The particular depth is dependent on a variety of factors, such as depth of the hydrocarbon bearing earth formation for which the survey is being performed, and the frequency of the interrogating energy used to probe the earth formation. In order to achieve the desired depth, some related art systems use devices known as “suppressors” which tend to dive with motion through the water. Such suppressors also contribute to required towing force.
The towing force associated with a large marine survey may be large. The amount of fuel used by the tow vessel is proportional to towing force developed by the tow vessel. It follows that reduction in towing force used may result in reduced overall cost of performing a marine survey.